Messages in this thread | | | Subject | Re: [PATCH v7 2/2] ARM: ftrace: Add MODULE_PLTS support | From | Florian Fainelli <> | Date | Fri, 12 Mar 2021 10:35:42 -0800 |
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On 3/12/21 9:24 AM, Qais Yousef wrote: > Hi Alexander > > On 03/10/21 18:17, Alexander Sverdlin wrote: >> Hi! >> >> On 10/03/2021 17:14, Florian Fainelli wrote: >>>>>>> I tried on 5.12-rc2 and 5.11 but couldn't reproduce the problem using your >>>>> I still can't reproduce on 5.12-rc2. >>>>> >>>>> I do have CONFIG_ARM_MODULE_PLTS=y. Do you need to do something else after >>>>> loading the module? I tried starting ftrace, but maybe there's a particular >>>>> combination required? >>>> You need to load a BIG module, so big that it has no place in the modules area >>>> any more and goes to vmalloc area. >>> You absolutely need a very big module maybe more than one. When I tested >>> this, I could use the two proprietary modules (*sigh*) that I needed to >>> exercise against and loading one but not the other was not enough to >>> make the second module loading spill into vmalloc space. >> >> Here is what I use instead of these real world "proprietary" modules (which of course >> were the real trigger for the patch): >> >> https://www.spinics.net/lists/arm-kernel/msg878599.html > > I am testing with your module. I can't reproduce the problem you describe with > it as I stated. > > I will try to spend more time on it on the weekend.
Alexander, do you load one or multiple instances of that fat module?
The test module does a 6 * 1024 * 1024 / 2 = 3 million repetitions of the "nop" instruction which should be 32-bits wide in ARM mode and 16-bits wide in Thumb mode, right?
In ARM mode we have a 14MB module space, so 3 * 1024 * 1024 * 4 = 12MB, which should still fit within if you have no module loaded, however a second instance of the module should make us spill into vmalloc space.
In Thumb mode, we have a 6MB module space, so 3 * 1024 * 1024 * 2 = 6MB so we may spill, but maybe not.
I was not able to reproduce the warning with just one module, but with two (cannot have the same name BTW), it kicked in. -- Florian
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